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Hydrogen bonding interactions and miscibility studies of poly(amide)/poly(vinyl pyrrolidone) blends containing mangiferin

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Abstract

Miscibility studies of amorphous poly(amide)/poly(vinyl pyrrolidone) (PA/PVP) blends containing a crystalline phytochemical called “mangiferin” have been carried out using differential scanning calorimetry, Fourier transformed infrared spectroscopy and polarized optical microscopy. The binary blends of PA/PVP prepared from dimethylsulfoxide solutions were found to be completely miscible showing a systematic movement of a single glass transition temperature over the entire composition range. The FTIR study indicated the occurrence of cross-hydrogen bonding interactions between PA and PVP, which may be responsible for complete miscibility of the PA/PVP pair. Moreover, cross-hydrogen bonding promotes miscibility in binary blends of PA/mangiferin and PVP/mangiferin. However, the addition of mangiferin to PA/PVP blends has resulted in liquid–liquid phase separation between PA/mangiferin and PVP/mangiferin phases due to the preferential affinity of mangiferin to PVP than to PA. With increasing mangiferin concentration, liquid–liquid phase segregations occur between PA+mangiferin and PVP+mangiferin phases in addition to the solid–liquid phase transition of mangiferin crystals. Lastly, a ternary morphology phase diagram of the PA/PVP/mangiferin blends was established, which exhibited various coexistence regions such as isotropic, liquid+liquid, liquid+crystal, liquid+liquid+crystal, and solid crystal regions.

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... °C, corresponding to the loss of bound water and the melting point of MGF, respectively [69,74]. With a higher proportion of MGF (1:1), the PMix MGF-copolymers had a relatively sharp melting peak, signifying phase separation [74]. ...
... °C, corresponding to the loss of bound water and the melting point of MGF, respectively [69,74]. With a higher proportion of MGF (1:1), the PMix MGF-copolymers had a relatively sharp melting peak, signifying phase separation [74]. Interestingly, the endothermic peak of P123 decomposition disappeared in the MMs and physical mixtures of QCT, while it was observed as a small peak in the MGF-MMs. ...
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Following oxidative stress, modifications of several biologically important macromolecules have been demonstrated. In this study we investigated the effect of a natural extract from Mangifera indica L (Vimang), its main ingredient mangiferin and epigallocatechin gallate (EGCG) on energy metabolism, energy state and malondialdehyde (MDA) production in a red blood cell system. Analysis of MDA, high energy phosphates and ascorbate was carried out by high performance liquid chromatography (HPLC). Under the experimental conditions, concentrations of MDA and ATP catabolites were affected in a dose-dependent way by H2O2. Incubation with Vimang (0.1, 1, 10, 50 and 100 microg/mL), mangiferin (1, 10, 100 microg/mL) and EGCG (0.01, 0.1, 1, 10 microM) significantly enhances erythrocyte resistance to H2O2-induced reactive oxygen species production. In particular, we demonstrate the protective activity of these compounds on ATP, GTP and total nucleotides (NT) depletion after H2O2-induced damage and a reduction of NAD and ADP, which both increase because of the energy consumption following H2O2 addition. Energy charge potential, decreased in H2O2-treated erythrocytes, was also restored in a dose-dependent way by these substances. Their protective effects might be related to the strong free radical scavenging ability described for polyphenols.
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Are soy isoflavones neuroprotective? Just how different is one species of Echinacea from another? Which phytochemicals will be effective as therapeutic agents in vivo? Supported by solid scientific research, Phytochemicals in Nutrition and Health helps provide answers to these and other probing questions concerning the mechanisms of action associated with beneficial phytochemical groups. It examines new areas such as the efficacy and safety of medicinal herbs, the use of biotechnology to manipulate and enhance the phytochemical profiles of various plants, and the pharmacokinetics of phytochemicals in humans. The editors also expand discussion presented in their previous books on phytochemicals. They explore new research on phytochemicals in the Vaccinium family (cranberries, blueberries and bilberries), wine, and oilseeds, and the biological activity of Echinacea in humans. Additional chapters present new information about isothiocyanates, lycopene, carotenoids other than beta-carotene, tocotrienols, and phytoestrogens. Highlighting phytochemicals that have significant potential for promoting health or preventing disease, Phytochemicals in Nutrition and Health expands discussions of appropriate research methodologies and new technologies in this exciting field.
Article
Miscibility studies on blends of poly(p-phenylene terephthalamide) (PPTA) and amorphous nylon copolymer have been undertaken using infra-red spectroscopy, optical microscopy and light scattering. Various blend films coagulated from methane sulphonic acid solution in water were yellowish, but transparent. The films turned translucent upon heating. Well developed spinodal structures were seen under the optical microscope and a scattering halo developed in the light scattering examination. A cloud point phase diagram was established subsequently. The phase behaviour is reminiscent of a lower critical solution temperature in character. Infra-red studies show a systematic movement of a single amide band from 1639 to 1655 cm -1 and an N - H stretching band from 3314 to 3329 cm -1 with blend composition, suggesting the occurrence of cross-hydrogen bonding between PPTA and amorphous nylons.
Article
The isolation and characterization of the chemical constituents of different parts of Mangifera indica, sound and infected with two pathogenic fungi, viz. Aspergillus niger and Fusarium moniliformae, are described. Natural occurrence of two polyketideshikimate-derived depsides is reported for the first time. Additionally, a number of xanthones, flavonoids, triterpenes and amino acids, not encountered before in this species, are reported. The co-occurrence of mangiferin, 1,3,6,7-tetra- and 1,3,5,6,7-pentaoxygenated xanthones and the quantitative variation of the latter two compounds with the growing of the plant and during the fungal infection are biochemically significant. The protector role of the flavonoids and other C15 metabolites to M. indica from the ingress of the fungal hyphae is indicated. The two pathogenic fungi secreted a number of mycotoxins in different parts of the host species during its vegetation and flowering periods. During the elaboration of these toxic metabolites, the host-pathogen interaction played an important role. Evidence is presented for A. niger as a mycotoxin producing fungus.
Article
A synthesis of mangiferin (I), 2-C-β-D-glucopyranosyl-1,3,6,7-tetrahydroxy-xanthone, is described.
Article
Hydroxylated (co)polymers form miscible blends with a wide variety of (co)polymers that contain proton acceptor groups, such as esters, ethers, pyridines, etc. The former strongly self-associate through the formation of OH/OH hydrogen bonded interactions, while the latter do not self-associate to any measurable extent. With appropriate self- and interassociation equilibrium constants and enthalpies of hydrogen bond formation, we have been able in the past to successfully predict the phase behavior of such hydrogen bonded polymer blends. At first glance, the vinyl pyrrolidone group appears to be just another proton acceptor and if the appropriate interassociation equilibrium constant value is determined we should be able to predict the phase behavior of hydroxylated (co)polymer blends with (co)polymers containing the vinyl pyrrolidone group. However, it is not that simple. Using infrared spectroscopy we demonstrate in this work that the pyrrolidone group strongly self-associates through transition dipole coupling. Ramifications to the determination of equilibrium constants, the free energy of mixing and the phase behavior of blends involving the vinyl pyrrolidone group are discussed.
Article
Polymer blends of poly(vinylphenol) (PVPh) with poly(vinylpyrrolidone) (PVP) were prepared by solution casting from the N,N-dimethylformamide (DMF) solution. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (NMR) were used to investigate the hydrogen bonding and miscibility behavior of the blend. This PVPh/PVP blend system has a single glass transition temperature over the entire composition range, indicating that this blend is able to form a miscible phase due to the formation of inter-hydrogen bonding between the hydroxyl of PVPh and the carbonyl of PVP. Furthermore, FTIR and solid-state NMR were used to study the hydrogen-bonding interaction between the PVPh hydroxyl group and the PVP carbonyl group at various compositions. According to the Painter−Coleman association model (PCAM), the interassociation constant for the PVPh/PVP blend is significantly higher than the self-association constant of PVPh, revealing that the tendency toward hydrogen bonding of the PVPh and PVP dominates the intra-hydrogen bonding of the PVPh in the mixture.
Article
The solution behavior of blends of an amorphous aromatic polyamide, nylon 3Me6T, in a homologous series of aliphatic polyamides has been interpreted in terms of a recently introduced mean-field binary-interaction model. Founded on the premise that the polyamides in question can be treated as copolymers composed appropriately of methylene, amide, and phenyl mers, it has been possible to estimate the segmental interaction parameters, χ ij. Using these values, a cartographic survey of the phase behavior of additional binary blends of aromatic/aliphatic polyamides has been conducted and found to correlate well with the experimental observations described here and in the literature.
Article
Amorphous poly(vinylpyrrolidone) (PVP) varying in molecular weight (MW) (10 000, 24 000, and 40 000) was used to study the effect of molecular weight on the glass transition temperature (Tg). Tg was measured by differential scanning calorimetry (DSC). Blends with several diluents (water, butylamine, glycine, hexanal, xylose, glucose, and lysine) were also analyzed and the effect of blend composition on Tg was evaluated. The effect of average molecular weight and of composition in the blends of PVP-plasticizer on Tg was well described by previously reported relationships developed for synthetic polymers. The quantitative results obtained can be used for formulation of mixtures with known Tg and for prediction of their behavior in storage.
Article
Mangiferin (MF) isolated from Anemarrhena asphodeloides Bunge rhizome, was tested for antidiabetic activity in KK-Ay mice, an animal model of type-2 diabetes. MF lowered the blood glucose level of KK-Ay mice 3 weeks after oral administration (p < 0.01). However, no effect on the blood glucose level in normal mice was seen, indicating that MF could be useful in treating type-2 diabetes. In addition, MF improved hyperinsulinemia and, on insulin tolerance test, reduced blood glucose levels of KK-Ay mice. From these findings, it seems likely that MF exerts its antidiabetic activity by decreasing insulin resistance.
Article
The moisture-induced plasticization of some amorphous polyamides in pure and blended form has been determined by calorimetric methods. The compositional dependence of the glass transition temperature of these polymer-diluent systems has been adequately accounted for using an existing predictive expression derived from both a conformational entropy and a thermodynamic treatment of the glass transition phenomenon. The success of this approach to account for the behavior of amorphous polyamide blends containing hydrophobic and hydrophilic constituents exemplifies the importance of compositional parameters in determining the overall response of morphologically complex hydrophilic polymers. The results add further credence to the simple plasticizing action of water in polar polymers irrespective of their chemical and physical constitution.
Article
Hydroxylated (co)polymers form miscible blends with a wide variety of (co)polymers that contain proton acceptor groups, such as esters, ethers, pyridines, etc. The former strongly self-associate through the formation of OH/OH hydrogen bonded interactions, while the latter do not self-associate to any measurable extent. With appropriate self- and interassociation equilibrium constants and enthalpies of hydrogen bond formation, we have been able in the past to successfully predict the phase behavior of such hydrogen bonded polymer blends. At first glance, the vinyl pyrrolidone group appears to be just another proton acceptor and if the appropriate interassociation equilibrium constant value is determined we should be able to predict the phase behavior of hydroxylated (co)polymer blends with (co)polymers containing the vinyl pyrrolidone group. However, it is not that simple. Using infrared spectroscopy we demonstrate in this work that the pyrrolidone group strongly self-associates through transition dipole coupling. Ramifications to the determination of equilibrium constants, the free energy of mixing and the phase behavior of blends involving the vinyl pyrrolidone group are discussed.
Article
Miscibility and crystallization of poly-p-phenylene terephthalamide (PPTA)/nylon 6 and nylon 66 composites prepared by coagulation of isotropic ternary sulfuric acid solutions were studied. The apparent crystallinity of nylon 6 and nylon 66 in molecular composites was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross-hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed.
Article
The objective of this work was to investigate hydrogen bonding interactions between a variety of glass-forming sugars and a model polymer, poly(vinylpyrrolidone) (PVP), in binary amorphous solid solutions, produced by lyophilization. The glass transition temperatures of the sugars and sugar–PVP colyophilized mixtures were assessed using differential scanning calorimetry. The hydrogen bonding interactions between each sugar and PVP were monitored using FT-Raman spectroscopy. Sucrose was found to hydrogen bond to a greater extent with PVP at a particular sugar:polymer ratio than the other disaccharides studied including trehalose and the trisaccharide raffinose. Maltodextrins showed a decreased tendency to hydrogen bond with the polymer compared to the lower molecular weight sugars. The extent of hydrogen bonding was found to correlate inversely with the glass transition temperature of the sugar, with the tendency to hydrogen bond decreasing as the Tg increased. The importance of hydrogen bonding interactions to the thermodynamics of mixing in amorphous solids is discussed.
Article
In the late 1950's free radicals and antioxidants were almost unheard of in the clinical and biological sciences but chemists had known about them for years in the context of radiation, polymer and combustion technology. Daniel Gilbert, Rebeca Gerschman and their colleagues related the toxic effects of elevated oxygen levels on aerobes to those of ionizing radiation, and proposed that oxygen toxicity is due to free radical formation, in a pioneering paper in 1956. Biochemistry owes much of its early expansion to the development and application of chromatographic and electrophoretic techniques, especially as applied to the study of proteins. Thus, superoxide dismutase (SOD) enzymes (MnSOD, CuZnSOD, FeSOD) were quickly identified. By the 1980's Molecular Biology had evolved from within biochemistry and microbiology to become a dominant new discipline, with DNA sequencing, recombinant DNA technology, cloning, and the development of PCR representing milestones in its advance. As a biological tool to explore reaction mechanisms, SOD was a unique and valuable asset. Its ability to inhibit radical reactions leading to oxidative damage in vitro often turned out to be due to its ability to prevent reduction of iron ions by superoxide. Nitric oxide (NO·) provided the next clue as to how SOD might be playing a critical biological role. Although NO· is sluggish in its reactions with most biomolecules it is astoundingly reactive with free radicals, including superoxide. Overall, this high reactivity of NO· with radicals may be beneficial in vivo, e.g. by scavenging peroxyl radicals and inhibiting lipid peroxidation. If reactive oxygen species are intimately involved with the redox regulation of cell functions, as seems likely from current evidence, it may be easier to understand why attempts to change antioxidant balance in aging experiments have failed. The cell will adapt to maintain its redox balance. Indeed, transgenic animals over-expressing antioxidants show some abnormalities of function. There must therefore be a highly complex interrelationship between dietary, constitutive, and inducible antioxidants within the body, under genetic control. The challenge for the new century is to be able to understand these relationships, and how to manipulate them to our advantage to prevent and treat disease.
Article
Progress in membrane and membrane process development have contributed to the continuous improvement of the extracorporeal treatment of renal failure during the last 40 years. Today membranes can be adapted to the specific needs required by their clinical application. Synthetic structures like the polyamide membranes offer a wide range of possibilities in performance and hemocompatibility, due to: (1) the use of block polymers or polymer blends and mixtures, and (2) modification of membrane structure, pore size and porosity, due to changes of the preparation process. However, further improvements are still required to achieve the ultimate goal of matching the performance of biological membranes.
Article
By means of a transaortal injection of a gelatine ink mixture, a manifold mucosa to muscularis blood flow ratio was proved. In addition, the treatment of hypo- and hypertonic NaCl by the rat urinary bladder has been studied at 0.3-, 0.6- and 0.9-ml filling levels in conjunction with continuous bladder pressure recording. With distension an increased permeability to NaCl (efflux) and/or water (influx) was found in hypertonic conditions. In order to demonstrate this, the decreasing surface to volume ratio with distension has to be considered. Final urea concentrations in hypertonic media significantly exceeded those in hypotonic probes. The phenomenon has been hypothetically attributed to the existence of an arteriovenous counter current exchange within mucosal vessels. In comparison to hypotonic bladder contents, hypertonic media increased basic bladder pressures and phasic pressure amplitudes preferably at the 0.9-ml level. Hence, in context with an increased permeability, distension favors access of the bladder content to detrusor nerve and muscle cells thereby facilitating their excitability.
Article
The effect of mangiferin, a tetrahydroxy pyrrolidone saponin extracted from the leaves of mango (Mangifera indica), against herpes simplex virus type 2 (HSV-2) in vitro was studied. The 50% effective concentration (EC50) of it against HSV-2 plaque formation in HeLa cells was 111.7 micrograms.ml-1, and the concentrations of 33 and 80 micrograms.ml-1 reduced the virus replicative yields by 90% (EC90) and 99% (EC99), respectively. The therapeutic index (IC50/EC50) was 8.1. Mangiferin did not directly inactivate HSV-2. The results of the drug addition and removal tests suggest that mangiferin inhibits the late event in HSV-2 replication.
Article
Free radicals and antioxidants are widely discussed in the clinical and nutritional literature. Antioxidants are needed to prevent the formation and oppose the actions of reactive oxygen and nitrogen species, which are generated in vivo and cause damage to DNA, lipids, proteins, and other biomolecules. Endogenous antioxidant defenses (superoxide dismutases, H2O2-removing enzymes, metal binding proteins) are inadequate to prevent damage completely, so diet-derived antioxidants are important in maintaining health. Many dietary compounds have been suggested to be important antioxidants: The evidence for a key role of vitamins E and C is strong, but that for carotenoids and related plant pigments is weaker. Interest is also growing in the role of plant phenolics, especially flavonoids. Some antioxidants can exert prooxidant effects in vitro, but their physiological relevance is uncertain. Experimental approaches to the optimization of antioxidant nutrient intake are proposed.
Article
A series of xanthone derivatives was synthesized and tested in-vitro for their ability to inhibit aggregation of rabbit washed platelets and human platelet-rich plasma (PRP) induced by various inducers. 2-Prenyloxyxanthone showed the most potent inhibition of rabbit washed platelet aggregation induced by arachidonic acid (IC50 = 10.2 μM). Of the compounds tested in human PRP, 2-[3 (propylamino)-2-hydroxypropoxy]xanthone (4) hydrochloride salt exhibited the most potent inhibition of platelet aggregation induced by adrenaline (IC50 = 4.4 μM), whereas in evaluation of mouse antithrombotic activity, compound 4 exhibited the most potent protection of mice from thrombotic challenge. Compound 4, 2-[3-(isopropylamino)-2-hydroxypropoxylxanthone hydrochloride salt and 2,5 dihydroxyxanthone suppressed the secondary aggregation induced by adrenaline in human PRP. We conclude that the antiplatelet effects of these compounds are mainly due to an inhibitory effect on thromboxane formation.
Article
Mangiferin, a C-glucosylxanthone (1,3,6,7-tetrahydroxyxanthone-C2-beta-D-glucoside) purified from plant sources was shown to have in vivo growth-inhibitory activity against ascitic fibrosarcoma in Swiss mice. Following in vivo or in vitro treatment, it also enhanced tumor cell cytotoxicity of the splenic cells and peritoneal macrophages of normal and tumor-bearing mice. In vitro treatment of the splenic cells of tumor-bearing mice with mangiferin resulted in augmented killing of tumor cells, both resistant and sensitive to natural killer cells. Mangiferin was also found to antagonize in vitro the cytopathic effect of HIV. The drug appears to act as a potent biological response modifier with antitumor and antiviral effect.
Article
Mangiferin (MF) and its glucosides (mangiferin-7-O-beta-glucoside) (MG) isolated from Anemarrhena asphodeloides Bunge rhizome, were tested for their antidiabetic activity in KK-Ay mice, an animal model of non-insulin-dependent diabetes mellitus (NIDDM). MF and MG lowered the blood glucose level of KK-Ay mice after oral administration. However, no affect on the blood glucose level in normal mice was seen, indicating that MF and MG are useful in treating NIDDM. In addition, MF or MG improved hyperinsulinemia in KK-Ay mice. From these findings, it seems likely that MF and MG exert their its antidiabetic activity by increasing insulin sensitivity.
Article
The effects of twelve aminoalkanolic derivatives of xanthone on platelet aggregation have been evaluated. Five from them inhibited thrombin-induced platelet aggregation. The most active compound was R-(+)-2-N-(7-chloro-2-xanthonemethyl)-2-N-methylamino-1-butanol [IV] which, at a concentration of 40 micrograms/ml, nearly completely inhibited the aggregation concentration (TAC) of thrombin.
Article
A number of Thai medicinal plants, recommended as remedies for herpesvirus infection and have been used in primary health care were investigated for their intracellular activities against herpes simplex viruses (HSV). Centella asiatica L., Maclura cochinchinensis Cornor, and Mangifera indica L. contained both anti-HSV-1 and -2 activities, as determined by plaque inhibition assay. An inhibition of the production of infectious HSV-2 virions from infected Vero cells could also be demonstrated. Combinations of each of these reconstituted extracts with 9-(2-hydroxyethoxymethyl) guanosine (acyclovir; ACV) resulted either in subadditive, additive, or synergistic interaction, against HSV-2, depending on the dose of ACV used; mixture of C. asiatica and M. indica exerted an additive effect in a similar assay. Furthermore, the inhibitory effects of these plant extracts were also substantiated by flow cytometric analysis of virus-specific antigens in the infected cells. The active constituent present in C. asiatica extract was determined to be asiaticoside while in M. indica was mangiferin. Thus, these data suggest therapeutic potential of these plant extracts.
Article
We compared the protective abilities of Mangifera indica L. stem bark extract (Vimang) 50-250 mgkg(-1), mangiferin 50 mgkg(-1), vitamin C 100 mgkg(-1), vitamin E 100 mgkg(-1)and beta -carotene 50 mgkg(-1)against the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced oxidative damage in serum, liver, brain as well as in the hyper-production of reactive oxygen species (ROS) by peritoneal macrophages. The treatment of mice with Vimang, vitamin E and mangiferin reduced the TPA-induced production of ROS by the peritoneal macrophages by 70, 17 and 44%, respectively. Similarly, the H(2)O(2)levels were reduced by 55-73, 37 and 40%, respectively, when compared to the control group. The TPA-induced sulfhydryl group loss in liver homogenates was attenuated by all the tested antioxidants. Vimang, mangiferin, vitamin C plus E and beta -carotene decreased TPA-induced DNA fragmentation by 46-52, 35, 42 and 17%, respectively, in hepatic tissues, and by 29-34, 22, 41 and 17%, in brain tissues. Similar results were observed in respect to lipid peroxidation in serum, in hepatic mitochondria and microsomes, and in brain homogenate supernatants. Vimang exhibited a dose-dependent inhibition of TPA-induced biomolecule oxidation and of H(2)O(2)production by peritoneal macrophages. Even if Vimang, as well as other antioxidants, provided significant protection against TPA-induced oxidative damage, the former lead to better protection when compared with the other antioxidants at the used doses. Furthermore, the results indicated that Vimang is bioavailable for some vital target organs, including liver and brain tissues, peritoneal exudate cells and serum. Therefore, we conclude that Vimang could be useful to prevent the production of ROS and the oxidative tissue damages in vivo.
Article
Whereas second-generation biomaterials were designed to be either resorbable or bioactive, the next generation of biomaterials is combining these two properties, with the aim of developing materials that, once implanted, will help the body heal itself.
Article
This study investigated the effects of the natural polyphenol mangiferin (MA) on superoxide anion (O(2)(-)) production, xanthine oxidase (XO) activity, vascular contractility, inducible nitric oxide synthase (iNOS) mRNA levels, tumour necrosis factor-alpha (TNF-alpha) mRNA levels, and tumour growth factor-beta (TGF-beta) mRNA levels. O(2)(-) was generated by the hypoxanthine-xanthine oxidase (HX-XO) and phenazine methosulphate (PMS)-NADH systems. XO activity was determined by measurement of uric acid production with xanthine as substrate. Vascular contraction experiments were performed with intact rat aortic rings. iNOS, TNF-alpha and TGF-beta gene expression in rat macrophages stimulated in vivo with 3% thioglycollate and in vitro with 100 ng/mL lipopolysaccharide and 10U/mL of interferon-gamma were evaluated semiquantitatively by the retrotranscriptase-polymerase chain reaction. MA at 10-100 microM, like the known O(2)(-) scavenger superoxide dismutase (1U/mL), scavenged O(2)(-) produced by the HX/XO and PMS-NADH systems. By contrast MA at 1-100 microM, unlike allopurinol (10 microM), was unable to inhibit XO activity. MA at 1-100 microM did not modify resting tone or the contractile responses elicited by 1 microM phenylephrine or 1 microM phorbol 12-myristate 13-acetate in rat aorta. MA at 1-100 microM, like dexamethasone (100 microM), decreased iNOS mRNA levels in activated macrophages. At 100 microM, MA also reduced TNF-alpha mRNA levels, but increased TGF-beta mRNA levels. These results thus indicate that MA is an O(2)(-) scavenger and that it inhibits expression of the iNOS and TNF-alpha genes, suggesting that it may be of potential value in the treatment of inflammatory and/or neurodegenerative disorders. In addition, the finding that MA enhances TGF-beta gene expression suggests that this polyphenol might also be of value in the prevention of cancer, autoimmune disorders, atherosclerosis and coronary heart disease.
Article
Flavonol O- and xanthone C-glycosides were extracted from mango (Mangifera indica L. cv. "Tommy Atkins") peels and characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry. Among the fourteen compounds analyzed, seven quercetin O-glycosides, one kaempferol O-glycoside, and four xanthone C-glycosides were found. On the basis of their fragmentation pattern, the latter were identified as mangiferin and isomangiferin and their respective galloyl derivatives. A flavonol hexoside with m/z 477 was tentatively identified as a rhamnetin glycoside, which to the best of our knowledge, has not yet been reported in mango peels. The results obtained in the present study confirm that peels originating from mango fruit processing are a promising source of phenolic compounds that might be recovered and used as natural antioxidants or functional food ingredients.
Article
The present study investigated the effects of orally administered Vimang (an aqueous extract of Mangifera indica) and mangiferin (the major polyphenol present in Vimang) on mouse antibody responses induced by inoculation with spores of microsporidian parasites. Inoculation induced specific antibody production with an exponential timecourse, peaking after about one month. Vimang significantly inhibited this antibody production from about three weeks post-inoculation, and most markedly by four weeks post-inoculation; by contrast, mangiferin had no significant effect. Determination of Ig isotypes showed that the IgM to IgG switch began about four weeks post-inoculation, with IgG2a predominating. Vimang significantly inhibited IgG production, but had no effect on IgM. Mangiferin did no affect either IgM or IgG2a, but significantly enhanced production of IgG1 and IgG2b. Neither Vimang nor mangiferin enhanced specific antibody secretion by splenic plasma cells from mice inoculated with microsporidian spores, whether administered in vivo before serum extraction or in vitro to the culture medium. Inoculation with spores induced splenomegaly, which was significantly reduced by Vimang and significantly enhanced by mangiferin. These results suggest that components of Mangifera indica extracts may be of potential value for modulating the humoral response in different immunopathological disorders.
Article
The polyphenol mangiferin (MA) has been shown to have various effects on macrophage function, including inhibition of phagocytic activity and of free radical production. To further characterize the immunomodulatory activity of MA, this study investigated its effects on expression by activated mouse macrophages of diverse genes related to the NF-kappaB signaling pathway, using a DNA hybridization array containing 96 NF-kappaB-related genes and on cytokine levels using a cytokine protein array. MA at 10 microM significantly inhibited the expression of (a) two genes of the Rel/NF-kappaB/IkappaB family, RelA and RelB (=I-rel), indicating an inhibitory effect on NF-kappaB-mediated signal transduction; (b) TNF receptor-associated factor 6 (Traf6), indicating probable blockage of activation of the NF-kappaB pathway by lipopolysaccharide (LPS), tumor necrosis factor (TNF), and interleukin 1 (IL-1); (c) other proteins involved in responses to TNF and in apoptotic pathways triggered by DNA damage, including the TNF receptor (TNF-R), the TNF-receptor-associated death domain (TRADD), and the receptor interacting protein (RIP); (d) the extracellular ligand IL-1alpha, again indicating likely interference with responses to IL-1; (e) the pro-inflammatory cytokines IL-1, IL-6, IL-12, TNF-alpha and RANTES (CCL5), and cytokines produced by monocytes and macrophages, including granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF); (f) other toll-like receptor proteins (in addition to Traf6), including JNK1, JNK2 and Tab1; (g) Scya2 (small inducible cytokine A2=monocyte chemoattractant protein 1); and (h) various intracellular adhesion molecules (ICAMs), and the vascular cell adhesion molecule VCAM-1, which is locally increased in atheromas. The inhibition of JNK1, together with stimulation of c-JUN (i.e. the Jun oncogene) and the previously reported superoxide-scavenging activity of MA, suggests that MA may protect cells against oxidative damage and mutagenesis. Taken together, these results indicate that MA modulates the expression of a large number of genes that are critical for the regulation of apoptosis, viral replication, tumorogenesis, inflammation and various autoimmune diseases, and raise the possibility that it may be of value in the treatment of inflammatory diseases and/or cancer.
Article
Mangiferin, a natural polyphenol is known to exhibit anti-inflammatory, antioxidant, and antiviral effects. However the molecular mechanism underlying these effects has not been well characterized. Because NF-kappaB plays an important role in these processes, it is possible that mangiferin modulates NF-kappaB activation. Our results show that mangiferin blocks tumor necrosis factor (TNF)-induced NF-kappaB activation and NF-kappaB-dependent genes like ICAM1 and COX2. The effect was mediated through inhibition of IKK activation and subsequent blocking of phosphorylation and degradation of IkappaBalpha. In addition, mangiferin inhibits TNF-induced p65 phosphorylation as well as translocation to the nucleus and also inhibits NF-kappaB activation induced by other inflammatory agents like PMA, ceramide, and SA-LPS. Mangiferin, similar to the other known antioxidants, NAC and PDTC, inhibits TNF-induced reactive oxygen intermediate (ROI) generation. Since intracellular glutathione (GSH) levels are known to modulate NF-kappaB levels, we measured the levels of GSH. Mangiferin enhances glutathione level by almost 2-fold more than other anti-oxidants, and at the same time it decreases the levels of GSSG and increases the activity of catalase. Depletion of GSH by buthionine sulfoximine led to a significant reversal of mangiferin effect. Hence mangiferin with its ability to inhibit NF-kappaB and increase the intracellular GSH levels may prove to be a potent drug for anti-inflammatory and antioxidant therapy. Mangiferin-mediated down-regulation of NF-kappaB also potentiates chemotherapeutic agent-mediated cell death, suggesting a role in combination therapy for cancer.
Article
Mangiferin, a naturally occurring glucosylxanthone, has been described as having antidiabetic, antiproliferative, immunomodulatory and antioxidant activities. In this study we report for the first time the iron-complexing ability of mangiferin as a primary mechanism for protection of rat liver mitochondria against Fe(2+)-citrate induced lipid peroxidation. Thiobarbituric acid reactive substances and antimycin A-insensitive oxygen consumption were used as quantitative measures of lipid peroxidation. Mangiferin at 10 microM induced near-full protection against 50 microM Fe(2+)-citrate-induced mitochondrial swelling and loss of mitochondrial transmembrane potential (DeltaPsi). The IC(50) value for mangiferin protection against Fe(2+)-citrate-induced mitochondrial thiobarbituric acid reactive substance formation (9.02+/-1.12 microM) was around 10 times lower than that for tert-butylhydroperoxide mitochondrial induction of thiobarbituric acid reactive substance formation. The xanthone derivative also inhibited the iron citrate induction of mitochondrial antimycin A-insensitive oxygen consumption, stimulated oxygen consumption due to Fe(2+) autoxidation and prevented Fe(3+) ascorbate reduction. Absorption spectra of mangiferin-Fe(2+)/Fe(3+) complexes also suggest the formation of a transient charge transfer complex between Fe(2+) and mangiferin, accelerating Fe(2+) oxidation and the formation of a more stable Fe(3+)-mangiferin complex unable to participate in Fenton-type reaction and lipid peroxidation propagation phase. In conclusion, these results show that in vitro antioxidant activity of mangiferin is related to its iron-chelating properties and not merely due to the scavenging activity of free radicals. These results are of pharmacological relevance since mangiferin and its naturally contained extracts could be potential candidates for chelation therapy in diseases related to abnormal intracellular iron distribution or iron overload.
Article
We propose a new theoretical scheme for the binary phase diagrams of crystal-liquid crystal mixtures by a combination of a phase field model of solidification, the Flory-Huggins theory for liquid-liquid mixing and Maier-Saupe-McMillan (FH-MSM) model for nematic and smectic liquid crystal orderings. The phase field theory describes the crystal phase transition of anisotropic organic crystal and/or side chain liquid crystalline polymer crystals while the FH-MSM model explains isotropic, nematic and smectic-A phase transitions. Self-consistent calculations reveal several possible phase diagram topologies of the binary crystal-liquid crystal mixtures. The calculated phase diagrams were found to accord well to the reported experimental results.
Article
A thermodynamically self-consistent theory has been developed to establish binary phase diagrams for two-crystalline polymer blends by taking into consideration all interactions including amorphous-amorphous, crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The present theory basically involves combination of the Flory-Huggins free energy for amorphous-amorphous isotropic mixing and the Landau free energy of polymer solidification (e.g., crystallization) of the crystalline constituents. The self-consistent solution via minimization of the free energy of the mixture affords determination of eutectic, peritectic, and azeotrope phase diagrams involving various coexistence regions such as liquid-liquid, liquid-solid, and solid-solid coexistence regions bound by liquidus and solidus lines. To validate the present theory, the predicted eutectic phase diagrams have been compared with the reported experimental binary phase diagrams of blends such as polyethylene fractions as well as polycaprolactone/trioxane mixtures.
Article
The impact of a polymer additive (polyvinylpyrrolidone, PVP) on hydrogen bonding in amorphous sugar matrices as well as on the glass transition temperature, T(g), were examined by temperature scanning Fourier transform infrared spectroscopy (TS-FTIR). An amorphous sugar matrix containing PVP was prepared by air-drying an aqueous solution of a sugar-PVP mixture. The hydrogen bonds in the sugar-PVP mixture (sugar-PVP and sugar-sugar hydrogen bonds) were analyzed from the IR peak positions corresponding to the stretching vibration of C==O groups of PVP and O--H groups of the sugar and the temperature dependence of the peak position of the O--H stretching vibration band. The addition of PVP to amorphous mono and disaccharides significantly lowered the extent of hydrogen bond formation while interactions between sugars and the PVP tended to prevent the disruption of hydrogen bonds due to increasing temperature, the magnitude of which was larger for larger oligomers. The T(g) value for the amorphous sugar was increased by the addition of PVP in many cases. As the size of sugar molecule became larger, the relative magnitude of the increased T(g) by PVP to the difference between the T(g) values for sugar alone and PVP alone became larger and then reached a certain level; it was slight in the case of glucose. Collectively, these results demonstrate that the magnitude of the impact of PVP on an amorphous sugar matrix strongly vary and are dependent on the types of sugar.